This invention relates to coaxial transmission cables for use in transmission of both conventional current and electromagnetic waves.
More particularly, this invention relates to a magnetically loaded transmission cable which has greater current carrying capabilities than previously known cables of equal size or alternatively the novel magnetically loaded transmission cable is capable of being made smaller in size and volume than previously known cables without causing increases in losses or time delay normally accompanying magnetic loading.
Heretofore, it was known that magnetically loading a coaxial transmission cable would increase the inductance of the line. As the inductance increases, characteristic impedance and the time delay increases in conventional coaxial cables. Heretofore, it was desirable to increase the inductance by magnetic loading to decrease attenuation even though such magnetic loading introduced hysteresis and eddy current losses and caused increases in time delay.
Magnetic loading materials spaced in the dielectric of coaxial cables are described in U.S. Pats. Nos. 2,787,656; 2,929,034 and 2,727,945. These and other magnetic loading teaching are generally concerned with high resistance and high permeability ferrites which by their structural nature are large or relatively thick and are not applicable for use for microminiature cables for solid loaded center conductors or as coatings on non loaded center conductors. Thin film magnetically coated center conductors have been employed in plated wire memory planes such as those shown in U.S. Pat. No. 3,460,114, however, such rigid planes are generally concerned with reducing the characteristic impedance of an unshielded insulated memory wire. Plated memory wires are not uniformly shielded and are designed to switch from one state to another by coupling magnetic fields.
There has long been a need to reduce the size and weight of flexible coaxial cables without increasing time delay or losses. Coaxial cable for high speed computers and communications equipment require minimized time delays as well as miniaturization. Major computer manufacturers and coaxial cable manufacturers have recognized this need but have not miniaturized conventional coaxial cables by magnetic loading because of the increase in time delay and losses. Since computer advances are often accomplished through faster operations embodied in solid state devices, the need for faster propagation of electrical pulse energy has become almost as important as miniaturization of the circuitry.